This invention relates to a flexure hinge assembly, and, more particularly, to such an assembly for connecting two rotary members while permitting universal movement through small angles between them.
A typical flexure hinge assembly of the prior art is disclosed in U.S. Pat. No. 3,811,172. Other prior art flexure hinge assemblies are referred to in the section entitled "Discussion of the Prior Art." The flexure hinge assemblies disclosed in U.S. Pat. No. 3,811,172 and in the other patents discussed infra each have two pair of diametrically opposed flexure hinges which permit universal movement through small angles between a central gimbal element portion and one end portion and have another two pair of oppositely disposed flexure hinges which permit universal movement through small angles between the central gimbal element portion and the other end portion.
Each flexure hinge comprise a pair of flexure blades with mutually orthogonal planes of flexure. One of each pair of flexure blades forming a flexure hinge is formed by a pair of circumferentially adjacent apertures in the wall of the inner tubular member, the other formed by a pair of circumferentially adjacent apertures in the outer tubular member. Also, in prior art teachings one of the flexure blades in each flexure hinge is oriented to contribute high axial strength along the longitudinal axis of the flexure hinge assembly and, the other blade of the pair is orthogonally oriented to provide the necessary radial stiffness required for an isoelastic suspension.
In cylindrical flexure hinge assemblies of the prior art, the tubular members are separated by flexure blades into an axially displaced driving portion, two gimbal portions and a driving portion. That is, these portions are axially displaced from each other along the longitudinal axis of the flexure hinge assembly. More particularly, axially displaced slots in the walls of each tubular member create a central gimbal portion which is connected to end portions by flexure blades. One end portion is used as a driving element for connecting to a drive shaft, the other as a driven element for mounting an inertial wheel known as a rotor element.
One common arrangement of the basic elements of a gyroscope comprises a motor supported on either side by bearings with the motor shaft projecting through one bearing for a distance sufficiently long for supporting a flexure hinge assembly and rotor mounted thereon. A flexure hinge having tubular driving, gimbal and driven elements formed by axially displaced slots in the tubular members has the disadvantage that the motor shaft projecting outwardly from the motor bearings has a certain amount of compliance which permits vibrations. The flexure hinge assembly and rotor mounted on the motor shaft, respectively, are therefore subject to any such vibrations. Spurious vibrations of the rotor are a source of error in the performance characteristics of a gyroscope.